基于pdf.js实现对pdf预览、批注功能、 保存下载pdf,适配H5,平板 踩坑记录
项目场景：
在APP端实现对pdf的批注,能够下载保存.能够获取批注信息同时能够重新渲染到pdf中.基于pdf.js-4.5.136版本源码实现。pc端能够正常预览下载pdf，构建打包后嵌入uniapp的webview遇到的问题记录
问题描述
将构建打包后的代码嵌入到uniapp中，运行出现Uncaught TypeError: Promise.withResolvers is not a function
10:30:27.935 同步手机端程序文件完成
10:30:29.098 正在启动HBuilder调试基座...
10:30:30.103 应用【移动端测试】已启动
10:30:30.294 [Object] {"errMsg":"reLaunch:fail page `/` is not found"} at permission.js:37
10:30:30.807 Uncaught TypeError: Promise.withResolvers is not a function at hybrid/html/web/viewer.mjs:24062解决方案：
源码构建打包用的gulp generic出现上述问题，采用gulp generic-legacy（兼容低版本浏览器）构建方式即可
问题描述
app.js:1173加载 PDF 时发生错误。 PDF.js v? (build: ?) Message: file origin does not match viewer's
app.js:1173 加载 PDF 时发生错误。PDF.js v? (build: ?)
Message: file origin does not match viewer's
解决方案：
将pdf.js中app.js的跨域拦截去掉重新构建， 或者直接修改构建后的viewer.js的validateFileURL方法
var validateFileURL = function (file) {if (!file) {return;}try {const viewerOrigin = new URL(window.location.href).origin || "null";if (HOSTED_VIEWER_ORIGINS.includes(viewerOrigin)) {// Hosted or local viewer, allow for any file locationsreturn;}const fileOrigin = new URL(file, window.location.href).origin;// Removing of the following line will not guarantee that the viewer will// start accepting URLs from foreign origin -- CORS headers on the remote// server must be properly configured.//去掉下面这段==========================/*if (fileOrigin !== viewerOrigin) {throw new Error("file origin does not match viewer's");}*/} catch (ex) {PDFViewerApplication._documentError("pdfjs-loading-error", {message: ex.message,});throw ex;}};
APP端下载pdf，需要更改下载方法，将pc端的下载方式改为移动端下载。通过uniapp的webview之间的通信，将文件流转成base64传到uniapp端处理下载保存到本地，更改viewer.j的下载方法
function download(blobUrl, filename) {//通过bloburl获取到blob对象再转成base64，传输到父页面uniapp端fetch(blobUrl).then(response => response.blob()).then(blob => {const reader = new FileReader();reader.readAsDataURL(blob);reader.onload = () => {const base64 = reader.result;uni.postMessage({data: {blob: base64},});} })//下面是pc端的下载方式，注释掉//const a = document.createElement("a");//if (!a.click) {// throw new Error('DownloadManager: "a.click()" is not supported.');//}//a.href = blobUrl;//a.target = "_parent";//if ("download" in a) {// a.download = filename;//}//(document.body || document.documentElement).append(a);//a.click();//a.remove();
}问题描述
在APP端下载，下载后的文件不含批注，只是源文件下载
解决方案：
通过跟踪源码，发现app端下载和pc端不同，
显然再APP保存文档的时候，出现异常，通过跟踪发现，批注存储序列化的时候出现分歧
get serializable() {if (this.#storage.size === 0) {return SerializableEmpty;}const map = new Map(),hash = new MurmurHash3_64(),transfer = [];const context = Object.create(null);let hasBitmap = false;for (const [key, val] of this.#storage) {//const serialized = val instanceof AnnotationEditor ? val.serialize(false, context) : val;//此处针对批注的value，强制序列化即可const serialized = val.serialize(false, context);if (serialized) {map.set(key, serialized);hash.update(`${key}:${JSON.stringify(serialized)}`);hasBitmap ||= !!serialized.bitmap;}}if (hasBitmap) {for (const value of map.values()) {if (value.bitmap) {transfer.push(value.bitmap);}}}return map.size > 0 ? {map,hash: hash.hexdigest(),transfer} : SerializableEmpty;}